Top-level connections

AI-generated Key Takeaways

• Blocks have three optional connections: nextStatement, previousStatement, and output.

• nextStatement and previousStatement connections are used to stack blocks vertically to create sequences.

• A statement block is a block with no output connector, usually having both previousStatement and nextStatement connections.

• nextStatement and previousStatement connections can be typed, but this is rarely utilized by standard blocks.

• An output connection allows a block to connect to value inputs, and blocks with an output cannot have a previous statement connection.

Blocks have three connections whose use is optional.

Statement Connections

Users can create sequences of blocks using the nextStatement and previousStatement connectors. In Blockly's standard layout, these connections are on the top and the bottom, with the blocks stacked vertically.

A block with a previous connector cannot have an output connector. The term statement block refers to a block with no output connector. A statement block will usually have both a previous connection and a next connection.

nextStatement and previousStatement connections can be typed, but this feature is not utilized by standard blocks.

Next Connection

Creates a point at the bottom of the block, so that other statements can be stacked below it. A block with a next connection but no previous connection usually represents an event, and can be configured to render with a hat.

JSON

Untyped:

{
  ...,
  "nextStatement": null,
}

Typed (rare):

{
  "nextStatement": "Action",
  ...
}

JavaScript

Untyped:

this.setNextStatement(true);  // false implies no next connector, the default

Typed (rare):

this.setNextStatement(true, 'Action');

Previous Connection

Creates a notch at the top of the block, so that it can be connected as a stack of statements.

Blocks with a previous connection cannot have an output connection.

JSON

Untyped:

{
  ...,
  "previousStatement": null,
}

Typed (rare):

{
  "previousStatement": "Action",
  ...
}

JavaScript

Untyped:

this.setPreviousStatement(true);  // false implies no previous connector, the default

Typed (rare):

this.setPreviousStatement(true, 'Action');

Output connection

A block may have a single output connection, represented as a male jigsaw connector on the leading edge. Outputs connect to value inputs. Blocks with an output are usually called value blocks.

JSON

Untyped:

{
  // ...,
  "output": null,
}

Typed:

{
  // ...,
  "output": "Number",
}

JavaScript

Untyped:

init: function() {
  // ...
  this.setOutput(true);
}

Typed:

init: function() {
  // ...
  this.setOutput(true, 'Number');
}

Blocks with an output connector cannot also have a previous statement notch.